If you are cooking frozen gyoza, do not defrost them. Cook them frozen following the same method below as you would cook fresh gyoza.
Heat a large frying pan with a lid (keep its lid off at this stage but within reach) with medium-high flame. Place 1 tablespoon of vegetable oil in the hot pan.
When the oil is hot, place the gyoza in the pan, flat side down, in two rows of six pieces, slightly overlapping each other. Fry until the side touching the pan turns light golden brown, then add 1/8 cup of water to the pan and quickly cover with a lid. Leave the dumplings to steam for 2 minutes or until most of the liquid has evaporated.
Take the lid off and grill for another 30 seconds to crisp. Make sure they don't burn.
Serve on a plate, crispy brown side up. Serve with the dipping sauce on the side.